This invention relates generally to the art of curved reflectors, such as those used as solar reflectors, and more particularly concerns a parabolic reflector which includes a reflecting surface which comprises a plurality of triangular sections and the framework to support the reflecting surface.
Generally, a paraboloid is an advantageous shape for a reflector as it has an inherent focusing capability, can be theoretically made quite large, and since it focuses on a point, instead of a line, can tolerate much greater focusing misalignment than other focusing reflectors. Thus, the design and construction of such a reflector is not as critical and hence generally less complex than other curved reflector systems, such as a trough system.
However, it is expensive and difficult to construct a parabolic reflecting surface from a single section of reflecting material, such as glass. An alternative to the single piece construction is the use of multiple sections. Parabolic reflectors have in fact previously been constructed from sections, but they have been impractical and inefficient, due to the geometry of the reflecting surface and the support structure therefore. One such technique is to project a plurality of equilateral triangles onto a parabolic surface, but the resulting structure is impractical and unstable, as its triangular sections vary widely in configuration, and the rim of the reflector is scalloped, which is a very difficult configuration to support.
When the parabolic configuration of a reflector is achieved by use of sections, plane reflecting members can be used, instead of curved members. This is desirable, as the cost of plane sections of glass is considerably less than curved glass. The use of slightly curved glass, however, would reduce the number of sections in the reflector, and would also increase the operating temperature of the unit, if desirable. It would reduce the cost of curved glass considerably if plane glass could be bent, but it has been heretofore accepted that plane glass cannot be bent to produce a curved surface, i.e. that only a minimal displacement of plane glass can be achieved before breakage occurs.
Thus, it is a general object of the present invention to provide a parabolic reflector and a supporting framework therefore which overcomes one or more of the disadvantages of the prior art noted above.
It is another object of the present invention to provide such a reflector apparatus which has a geometry particularly suitable for large dimension reflectors.
It is a further object of the present invention to provide such a reflector apparatus which comprises triangular sections which present approximately the same surface area relative to a point on the central axis of the reflector at infinity, i.e. relative to the sun.
It is an additional object of the present invention to provide such a reflector apparatus which is arranged so that its rim lies substantially in a single plane.
It is a still further object of the present invention to provide a system for bending plane sheets of glass so that they approximate a curve.
It is yet another object of the present invention to provide such a reflector apparatus in which otherwise plane sections of glass are bent and fitted together to form a substantially parabolic surface.